<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        var a = [];
        for (let i = 0; i < 10; i++) {
            a[i] = function() {
                console.log(i); //所以输出5
            };
        }
        a[5](); //就是只循环一次，a[i],i是什么就是什么
    </script>
</body>

</html>